Outlet valves must be installed in cisterns in such a manner as to allow their removal for service and repair. In a toilet suite that has a separate cistern and pan, the outlet valve has a threaded tail which passes through an opening in the bottom of the cistern and is fastened thereto by an external nut. A seal is placed in the potential leak path between the cistern interior and the valve. When the nut is unscrewed from the tail, the outlet valve can be removed from the cistern.
In a one piece toilet suite the underside of the cistern is concealed by a shroud that extends from the cistern to the pan. The shroud makes access to the underside of the cistern very difficult, particularly after the suite has been grouted to a bathroom floor.
One known arrangement which avoids having to access the underside of the cistern to remove the outlet valve uses the previously described nut to instead clamp a stainless steel mounting plate to the valve tail, with a seal therebetween. A second seal is then placed on the underside of the mounting plate. The mounting plate, and thus the outlet valve, is then fixed to the cistern via two captive bolts in the base of the cistern that pass through holes in the mounting plate.
This known arrangement has several disadvantages. Firstly, an additional potential leak path is introduced at the second seal between the mounting plate and the cistern. Secondly, the stainless steel plate is expensive to manufacture and time consuming to install. Thirdly, the addition of the mounting plate and the second seal increases the overall height of the outlet valve, which can limit the range of cisterns to which it may be fitted.